<p>A hierarchy of questions and answers about the features of distributed computing systems (DCSs) leads to an overall system description that facilitates system comparisons. The taxonomy uses terminology from an object-based model of DCSs and emphasizes the runtime services the DCS provides to applications. It is based on the division of DCS issues into three distinct categories: threads object properties and separation. The threads subtree explores the creation, the number, and the control of threads in the DCS. The object properties subtree explores DCS features that are defined for objects in isolation. The separation subtree explores issues that arise because there are many objects in the DCS. To describe a specific DCS, a taxonomy user traces paths through the hierarchy.</p>